Portable devices such as smartphones, tablets, console games or e-book readers, usually utilise multiple supply voltages to power up different internal modules.
Some applications require bipolar power supplies with different regulated voltages, meaning that both positive voltage and negative voltage are needed.
Audio module and display panel are some of examples compliant with the foregoing.
For instance, Active Matrix Organic Light Emitting Diodes (AMOLED) display panel, which is a good candidate for portable devices due to its high display quality (i.e. brightness, contrast, vividness and wide viewing angle) and low power consumption requires the supply of both a positive voltage of 4.6 V and a negative voltage ranging from −1.5 V to −7 V to operate properly.
A power converter such as a Single Inductor Bipolar Output (SIBO) converter may be used to provide such positive and a negative power supply.
A converter is proposed in document (1): TEXAS INSTRUMENTS, TPS65136. Single Inductor Multiple Output Regulator for AMOLED. http://www.ti.com/lit/ds/symlink/tps65136.pdf (849 KB). 7 Jul. 2008.
However, the converter of document (1) is not able to operate properly with stability if the load current asymmetry between the negative output current and the positive output current is greater than 30%, meaning that the difference in current at each output needs to stay in close range.
To summarize, the control of a SIBO-Boost converter adapted to generate required positive output voltage and negative output voltage is not adequately addressed by known techniques.
A possible controller that might be used to solve the above problem is described in document (2) WO2012/032176 wherein it is disclosed a power stage that might be adapted to output a positive output voltage and a negative output voltage. While working satisfactorily, the solution described in document (2) may still be improved to better meet the ever increasing requirements of wireless applications.